Method is for preparation of test piece for use in durability test of engine block which contains cylindrical hollow formations separated from each other by intermediate walls

(54) Name: Engine life span test (56) Published publications: - (47) Abstract:

The object of the present invention is to provide an alternative method for the lifetime testing of an engine block. The engine block comprises cylindrical cavities, which cylindrical holdings are separated from each other by intermediate cradles, each intermediate wall comprising a bolt hole. The method comprises the step of removing a test piece from a region of the intermediate wall of the engine block so that the test piece comprises butthole.

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Summary

The object of the present invention is to provide an alternative method for life-time testing of a motor block. The engine block comprises cylindrical cavities, which cylindrical cavities are separated from each other by intermediate walls, each intermediate wall comprising a bolt hole. The method comprises the step of: removing a sample piece from a region of the intermediate wall of the engine block so that the sample piece includes the bolt hole.

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technology Area

The present invention relates to a method for preparing a test piece for use in a life-long test using a motor block, a method for preparing a test assembly for use in a life-long test using a motor block, a method for performing a life-long test using a motor block and a motor block associated with a load / life curve generated by the procedure for performing a life-long test.

technology Background

To test and compare the service life of engine block walls in engines, several solutions have emerged. One example is using the principle of the so-called Hydro Pulse

Testing of engine blocks. This is accomplished by filling the cylinders with hydraulic oil. High pressure hydraulic oil is pressed into the cylinder at a frequency of up to about 15 Hz. The principle of Hydro Pulse Testing is that internal dummy components are used to apply a pulsating force to the engine block walls. This pulsating force simulates the most significant forces on the engine block structure under operating conditions. A number of samples are subjected to pulsating fatigue at different loads for failure, or until a predetermined number of pulsating cycles has ended. The test results are plotted in a pressure / lifetime diagram. By using a well-known mathematical method, such as a Wöhler diagram, a curve is adjusted to the test results. Accordingly, a pressure / life curve describes the fatigue behavior of the tested material or component under constant amplitude. However, there are some problems with the Hydro Pulse Testing method. The very high oil pressure required increases the risk of significant damage to equipment in the event of a leak. It is also difficult to obtain the high oil pressures that are lined today, and if the trend to increase cylinder pressure in production engines during combustion continues, it will be even more difficult in the future. The maximum frequency of testing is comparatively low. The procedure is very time-consuming, a seven-series test series lined to make a reliable pressure / life curve takes about 4 weeks to run.

JP11316174 discloses a test method and a test device of a motor block bearing part, wherein the life-time testing of a motor block bearing part is performed by fixing a supporting part for supporting an axle arranged in the supporting part to be tested by a vibration generating plate. Although this process solves the problem of high oil pressure mentioned above, it has some drawbacks.

In the Hydro Pulse Testing case and in procedure in JP11316174, the areas around two bolt holes are subjected to stress at the same time. This means that when one of them breaks, so is the other

528 669 unusable for lifetime evaluation. At most, there are only three test results per block. In a series of about 20 test results, which is common when making a reliable load / life curve, seven engine blocks are lined. The consequence of this is that the Hydro Pulse Testing case and the case described in JP11316174, have the problem that the engine block consumption is very high. An engine block is very expensive and requires a high energy consumption to produce, and a high consumption of them therefore makes these test procedures very expensive.

Description of the invention

It is therefore an object of the invention to provide an alternative method for life-time testing of an engine block.

In accordance with the invention, this object is achieved by a method of preparing a test piece for use in a life-long test using an engine block, the engine block comprising cylindrical cavities, which cylinder cavities are separated from each other by intermediate walls, each intermediate wall comprising a bolt holes. The method comprises the steps of: removing a sample piece from a region of the intermediate wall of the engine block so that the sample piece includes the bolt hole.

In accordance with the invention, this object is further accomplished by a method of preparing a sample assembly for use in a lifetime test using an engine block, using a sample bit prepared by the sample bit preparation method of the invention. The method includes the step of engaging a dummy assembly with the bolt hole in the specimen, constituting the specimen assembly.

In accordance with the invention, this object is further achieved by a method for performing a life-long test by using an engine block using a sample assembly prepared by means of the sample assembly preparation method according to the invention. The method comprises the step of subjecting the sample assembly to a pulsating fatigue sample.

In accordance with the invention, this object is further achieved in that an engine block is associated with a load / life curve generated by the test method according to the invention.

Due to the fact that the test pieces are removed from the engine block to make a life-long test in accordance with the invention, instead of applying dummy components, test elements, etc., directly to an undisturbed engine block, an alternative method of life-time testing of a engine block is provided.

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An advantage of the present invention is that each bolt hole area in the engine block contributes to the final load / life curve, and can therefore be subjected to an individual load case of the operator's choice.

Another advantage of the invention is that it provides a lower cost of testing because fewer engine blocks are removed from production.

Another advantage of the invention is that the pulsating frequency can be increased, which provides increased sample capacity due to shorter lead times.

Another advantage of the invention is that the test procedure provides a less complex load case locally, and a more precise stress control in the important area.

Another advantage of the invention is that it provides an opportunity to perform effective studies of casting parameters, as well as other parameters.

Brief description of the drawings

Figure 1 is a schematic overview of an engine block for testing in accordance with the invention.

Figure 2 is a cross section at line AA of Figure 1.

Figure 3 is a perspective view of a sample bit used in the method according to the invention.

Figure 4 is a perspective view of a dummy assembly used in the method according to the invention.

Figure 5 is a perspective view of a sample assembly used in the method of the invention.

Figure 6 is a perspective view of a dummy assembly inserted into a special drawing device used in the method according to the invention.

Figure 7 is a schematic overview of an axial hydraulic fatigue test rig used in the method according to the invention.

Figure 8 is a flowchart depicting a method of preparing a test piece in accordance with the invention.

Figure 9 is a flowchart depicting a method for preparing a sample assembly in accordance with the invention.

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Figure 10 is a flowchart depicting a method for performing a lifetime test in accordance with the invention.

Methods of Carrying Out the Invention

Instead of applying dummy components, test elements, etc., directly to an undisturbed engine block to make life-long tests, sample pieces are removed from the engine block to perform a life-long test in accordance with the invention. Fully made engine blocks can be used to make the test pieces. Figure 1 shows a schematic overview of a motor block 100 seen from above. The engine block 100 may be of different types, such as, for example, Inline or V blocks. In this example, engine block 100 is an inline engine block having six cylindrical cavities 105, which six cylindrical cavities 105 are separated from each other by intermediate walls. The engine block 100 includes bolt holes 110. The bolt hole 110 may be a bolt hole for overflow to main bearings or other types of bolt holes, such as cylinder head bolt holes, which are often threaded inside. The bolt holes 1110 are intended to receive bolts, such as bolts for assault to main bearings, which bolts for assault to main bearings in turn hold a crankshaft in place. The construction of the engine block 100 is such that cracks under test conditions regularly occur at a thread or at the lower radius of the bolt holes 110 in the intermediate wall. Therefore, the sample bit is removed to include a bolt hole 110. Usually, and in this example, there are two bolt holes 110 for main bearing overlays in each intermediate wall. Therefore, an area 115 including the intermediate wall is removed from the engine block 100. This can be accomplished by sawing with the aid of a cutting machine. The removed area 115 comprising the intermediate wall then comprises two bolt holes 110.1 in this six-cylinder example, then five regions 115 including intermediate walls can be removed as depicted by dashed rectangles 115 in Figure 1.

Figure 2 depicts a cross section of the block motor 100 along line AA designated in Figure 1, including the intermediate wall 115 to be removed. A sample piece 120 is removed from a region of the intermediate wall 115, which sample includes a bolt hole 110. This can be accomplished by sawing with the aid of a cutting machine. As mentioned above, and which can also be seen in Figure 2, the intermediate wall 115 comprises two bolt holes 110. Therefore, two sample pieces can be removed from a removed intermediate wall 115, each sample piece 120 being removed from a region comprising a bolt hole 110 in this example with six cylinders, and with five intermediate walls 115 removed, ten sample pieces can be removed from one and the same engine block 100 .

Figure 3 depicts a perspective view of sample piece 120. The sample piece is removed so that the bolt hole 110 has its opening at a first end of the sample piece 120, and that the bolt hole 110 extends in an axial direction within the sample piece 120 for more than half the length of the sample piece 120. Bolt hole

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110 is marked by dashed lines in Figure 3. The test piece 120 includes a second end 132, the other end 132 of the test piece being suitably formed to engage an axial hydraulic fatigue test rig 185 (depicted in Figure 7). In order to force the cracks during the sample to originate from the bolt holes 110, a center portion 125 of the sample piece 120 is turned or cut into a circular cross-section, forming a cylindrical portion of the sample piece 120 such that the bolt hole 110 comprises sample piece 120 is coaxial with the cylindrical The sample piece 120, as shown in Figure 3. The length of the sample piece 120 may be, for example, 150-300 mm, preferably about 180 mm long. The other end 132 of the test piece forms a fixture region for gripping the axial hydraulic fatigue test rig. This second end 132 has a rectangular cross-section and has a length which can be varied depending on the type of fixture equipment and the possible need for the manufacture of stretching test pieces for evaluation of static material properties such as tensile boundary, elastic modulus etc. The middle portion 125 of the test piece 120, i.e., the circular cross-section of the test piece 120, may have a diameter of, for example, 28-36 mm, preferably 32 mm, and may be 40100 mm, preferably 60 mm long.

In the test procedure of the invention, a dummy assembly 135 is depicted in Figure 4. The word dummy is defined in this document as a replacement element, which is prepared for and used solely for testing, and which dummy element deceives the block motor 100 into believing that the element is a real element, such as tricking block engine 100 into believing that a dummy element is a proper assault to the main bearing. The dummy assembly 135 includes a dummy member 140 and a bolt 145. In this example, the dummy element 140 is a dummy overlay to the main bearing which is cylindrical. The dummy member 140 may also be another type of dummy member, such as a dummy cylinder head. The dummy member 140 includes a first end 146 and a second end 147. The dummy member 140 includes at its first end 146 a head 148, i.e. a portion having a diameter greater than the rest of the dummy member 140. The difference in level of the two different diameters, that is, of the head 148 and the rest of the dummy element 140, forms a lug 150. The lug 150 is meant to hook on a pulling device 155 (shown in Figure 6). The dummy element 140 further includes a through hole 160 in its axial direction. The hole 160 is marked with dashed lines in Figure 4. The bolt 145 may be a main bearing bolt or other type of bolt, such as a cylinder head bolt, and includes a head 165 at one end thereof and is threaded at its other end. The diameter of the head 165 is larger than the through-hole 160 in the dummy element 140, while the diameter of the remainder of the bolt 145 has a diameter less than the diameter of the through-hole in the dummy element 135. The bolt 145 is inserted through the hole 160 to a position where it is stopped. of head 165 of bolt 145. The assembled dummy member 140 and bolt 145 constitute the dummy assembly 135, which is shown in Figure 4.

With reference to Figure 5, then the main bearing 135 is then engaged with the bolt hole 110 in the sample piece 120, for example by screwing the bolt 145, projecting from the hole 160, into the

528 669 thread the bolt hole 110 in the sample piece 120. The main bearing 135 which engages the sample piece 120 constitutes the sample assembly 166. The bolt 145 engages the bolt hole 110 so that the second end 147 of the dummy element 140 abuts the surface of the first end 130 of the sample piece 120. If the gripping is performed by screwing, it is screwed in with the desired torque to simulate a realistic bias, typically from 50 Newton meters (Nm) plus 90 degrees offset to 200 Nm plus 90 degrees offset.

The main bearing 135 and the sample bit 120 which grip each other are then inserted into a special drawing device 155, shown in Figure. The pulling device 155 includes a first end 167 and a second end 168. The first end 167 is suitably designed to engage an axial hydraulic fatigue test rig. The pulling device 155 includes a cavity 170. The cavity 170 includes an aperture 175 at the other end 168 of the drawing device 155, the aperture 175 having a diameter greater than the smallest diameter of the dummy member 140, and may be narrower than the head 148 of the dummy member 140. The dummy member 140 engages the pulling device 155 by being inserted inside the cavity 170 by the pulling device 155, which has its head 148 inside the cavity 170, extending through the aperture 175 and which is hooked by the lug 150 of the head 148 when the head 148 has a too large a diameter to pass through the aperture 175 of the drawing device 155. the aperture 175 may also have a larger diameter than the head 148.1 in the case two specially designed fuse washers 178 can be used, between the inside of the aperture 175 and the lug 150 of the head 148 to prevent the head 148 from passing through the aperture 175. The main bearing 135 and the test piece 120 which grips in each other, that is, the sample assembly 166, is inserted into the drawing device 155. The pulling device 155 can be mounted in the axial hydraulic fatigue test rig before or after the main bearing 135 and the test piece 120 engaging each other are inserted into the pulling device 155. However, it can be easier to handle the engagement if it is mounted before the main storage 135 and the test piece 120 is inserted as gripping each other in the drawing device 155.

The test assembly 166 is mounted in an axial hydraulic fatigue test rig 185, depicted in Figure 7. One end of the test assembly made by the first end 167 of the pulling device 155 is mounted in a first mounting device 190 by the axial hydraulic fatigue test rig 185. It may be easy to handle if the first end 167 of the pulling device 155 is mounted in the axial hydraulic fatigue test rig prior to the main bearing 135 and the sample bit 120 engaging each other is inserted into the pulling device 155, as mentioned above. The other end of the test assembly made of the other end 132 of the test piece 120 is mounted in a second mounting device 190 of the axial hydraulic fatigue test rig 185. The sample bit 120 is then subjected to pulsating fatigue loads where R&gt; 0, for example 0.01-0.5, preferably 0.1, where R is the ratio between a minimum load and a maximum load between which the load varies, i.e., pulses. To do one

528 669 lifetime samples and form a load / life curve for an engine block, then a series of samples are fed at different loads, for example, 3-35 samples, preferably 20 samples.

The word life span in this document is defined as the number of cycles to break for a test piece. In an example using a gray iron engine block, the various loads may be such that the maximum load ranges used are selected between 50 and 80 kilos of Newton (kN). The minimum loads used are determined by the selected R-value.

The pulsating frequency can be from 1 Hz upwards. When the test time is to be kept as short as possible, it is preferable to use as high frequencies as 50 Hertz (Hz) which has been successfully tested. However, frequencies up to about 100 Hz may be possible to use. The test piece 120 can be entered up to a predetermined number of cycles, until! Example 5 * 10⁵-2*10⁷ cycles, preferably 2 * 10⁶ cycles, and then considered final run, that is, the test is stopped when the test piece 120 has run the predetermined number of cycles without breaking. In a reliable test series, the predetermined number of cycles is determined so that most of the samples yield before the predetermined number of cycles have been reached. The load level and the number of cycles to failure are recorded as test results for each sample. The test results are then plotted in a load / life curve. Finally, the load / life curve is used to compare the life characteristics of different engine blocks, for example blocks of different materials and structures.

As mentioned above, sample pieces can be taken from an inline engine block, which has six cylindrical cavities. This means that series of 20 samples only feed two engine blocks, which indicates a small consumption of engine blocks. A series of 20 samples using the frequency of 50 Hz and a predetermined number of cycles of 2 * 10® cycles only take about a week, which is a short time. This means a faster determination of the quality of the motherblood.

In this way, a motor block may have a load / life curve generated by the test procedures according to the invention. Different engine blocks or types of engine blocks can be tested in different test series generating and different load / life curves respectively.

The method of preparing a test piece 120 for use in a lifetime test using an engine block 100 in accordance with the invention will now be briefly described with reference to Figure 8. The method comprises the following steps:

801) The test piece 120 is removed from a region of the intermediate wall 115 of the engine block so that the test piece comprises the bolt hole 110.

802) A second end 132 of the test piece is formed 120 to be adapted to grip in an axial hydraulic fatigue test rig (185).

803) The center portion 125 of the test piece 120 is turned or cut into a circular cross-section, so that the bolt hole 110 included in the test piece 120 is coaxial with the turned or cut cylindrical portion 125 of the test piece 120.

804) The test piece 120 is formed to a length of 150-300 mm, preferably 180 mm.

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Process for preparing sample assembly 166 for use in a lifetime test using a motor block 100, in accordance with the invention, will now be briefly described with reference to Figure 9. The method uses a sample bit 120 prepared by the method according to process step 801. 804 above, and includes the steps of:

901) The dummy element 140 and the bolt 145 are assembled by inserting the bolt 145, through the hole 160 to a position where it is stopped by the head 165 of the bolt 145, where the assembled dummy element 140 and a bolt 145 constitute the dummy assembly 135.

902) The dummy assembly 135 engages the bolt hole 110 in the sample piece 120, constituting the sample assembly 166.

Process for performing a life-long test using engine block 100, in accordance with the invention, will now be briefly described with reference to Figure 10. The method uses a sample assembly 166 prepared by the method according to process steps 901-902 above, and comprises the steps to:

1001) The drawing device 155 is mounted in the axial hydraulic fatigue test rig

185.

1002) The test assembly 166 engages the drawing device.

1003) The test assembly 166 is mounted in the axial hydraulic fatigue test rig 185.

1004) The test composition 166 is subjected to a pulsating fatigue test.

The invention is not limited to the preferred embodiments described above. Various alternatives, modifications and equivalents can be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention as defined by the appended claims.

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