约翰逊弹性极限.pdf

Comparison of TEGOSTAR 738 with ASTM B 23 2 alloy Based on US measuring techniques The typical stress strain diagram of known bearing metals is curved over its whole length whereas the stress strain behaviour of TEGOSTAR 738 presents a marked linear range and the J A E L point lies just below 25 ultimate strength in com pression see Fig 1 That means that TEGOSTAR 738 contrary to all other bearing metals possesses a large elastic range approx 6 times larger than that of the alloy ASTM B 23 2 taking the 100 C J A E L values as reference This results in a considerable reduction of plastic deformation under high load and high temperature Fig 2 shows these creep characteristics of TEGOSTAR 738 as compared with ASTM B 23 2 alloy The creep intensity of TEGOSTAR 738 is 8 times lower Fig 3 shows the higher extended yield point as a function of the reduced TEGOSTAR layer thickness applied on the steel supporting body In general all bearing materials show this composite effect but it can only be utilized if the material possesses reduced creep characteristics like TEGOSTAR 738 ASTM B 23 does not give any data of the material properties regarding impact bearing capacity We tested this property and found that for TEGOSTAR 738 and ASTM B 23 2 alloy it lies on an equally high level Advantages of TEGOSTAR 738 as against ASTM B 23 2 alloy More than double compressive strength Greatly reduced creep intensity Longer service life of the friction bearings Higher utilizable compressive strength due to reduced layer thickness of the bearing metal High impact bearing capacity Suitability for all application ranges Environmentally compatible alloy without lead cadmium nickel and arsenic Fig 1 Chemical composition and physical properties of TEGOSTAR 738 and ASTM B 23 2 alloy Tin Antimony Copper Zinc Silver 20 C 100 C 20 C 100 C 20 C 100 C 20 C 100 C Deg F Deg C Deg F Deg C Deg F Deg C TEGOSTAR 81 3 12 0 6 0 0 6 0 1 7 35 12660 7020 11840 6530 19300 10300 26 14 458 235 680 360 970 540 ASTM B23 289 007 53 57 39610030003350110014900870024 512466241669354795424 Temp of Complete Lique faction Proper Pouring Temp Specific Gravity Alloy Grade Yield Point psi Brinell Hardness Melting Point Johnson s Apparent Elastic Limit psi J A E L Ultimate Strength in Compression psi Specified Nominal Composition of Alloys percent Fig 2 Creep characteristics of TEGOSTAR 738 and ASTM B 23 2 Fig 3 Higher extended yield point of TEGOSTAR 738 as a function of the reduced layer of bearing metal applied on steel 0 1 2 3 4 5 6 Time sec Load 15 MPa Temperature 100 C 212 F 100 000500 000 1 000 000 ASTM B23 2 TEGOSTAR Creep deformation 0 5 2 5 4 56 5 TEGOSTAR layer thickness mm 7000 14000 21000 28000 Extended Yield psi Temperature 100 C 212 F Remarks on the US measuring techniques In the U S A the ASTM standard is valid There are basic values and measuring techniques for representing material data which differ from European standards In Europe for example the permanent elongation limit or extended yield point respectively is usually defined at an elongation of 0 2 According to ASTM the corresponding yield point lies at an elongation of 0 125 The compressive strength is defined at a linear compression of 50 the corresponding ultimate strength in compression according at a linear compression of 25 The usual unit is psi 1 psi 0 0068948 N mm The J A E L value Johnson s Apparent Elastic Limit usual in the U S A is explained in the sketch below for torsional strain It applies analogously to tensile and compressive strain Johnson s Apparent Elastic Limit J A E L uses the straight line of a deformation which is for example 2 3 greater than the deformation measured and puts it as a tangent line against the measured defor