Finite Element Study on the Wear Performance of Movable Jaw Plates of Jaw Crushers after a Symmetrical Laser Cladding Path

At present, research on the influence of friction heat on the wear resistance of laser cladding layers is still lacking, and there is even less research on the temperature of laser cladding layers under different loads by a finite element program generator (FEPG). After a symmetrical laser cladding path, the wear performance of the moving jaw will change. The study of the temperature change of the moving jaw material in friction provides a theoretical basis for the surface modification of the moving jaw. The model of the column ring is built in a finite element program generator (FEPG). When the inner part of the column is WDB620 (material inside the cylinder) and the outer part is ceramic powder (moving jaw surface material), the relationship between the temperature and time of the contact surface is analyzed under the load between 100 and 600 N. At the same time, the stable temperature, wear amount, effective hardening layer thickness, strain thickness, and iron oxide content corresponding to different loads in a finite element program generator (FEPG) were analyzed. The results showed that when the load is 300 N, the temperature error between the finite element program generator (FEPG) and the movable jaw material is the largest, and the relative error is 4.3%. When the load increases, the stable temperature of the moving jaw plate increases after the symmetrical laser cladding path, and the wear amount first decreases and then increases. The minimum wear amount appears at a load of 400 N and a temperature of 340 °C; the strain thickness of the sample material increases gradually, and the effective hardening layer thickness increases. However, when the load reaches 400 N, the thickness of the effective hardening layer changes little; the content of Fe decreases gradually, and the content of FeO and Fe2O3 increases. The increase of the moving jaw increases in turn the temperature of the laser cladding layer of the test jaw material, which intensifies the oxidation reaction of the ceramic powder of the laser cladding layer.

Automated Behavioral Testing of Refactoring Engines

Refactoring is a transformation that preserves the external behavior of a program and improves its internal quality. To help developers in this task, current IDEs, such as Eclipse and NetBeans, automate a number of refactorings. However, implementing refactorings is a complex task, and so, even mainstream IDEs contain critical bugs. We propose an automated approach for testing of Java refactoring engines. Its key components are: JDOLLY, a Java program generator, and SAFEREFACTOR, a program for checking behavioral changes. The technique uses JDOLLY to generate programs as test inputs. For each generated program, it applies the refactoring by using the engine under test, and uses oracles based on SAFEREFACTOR to evaluate the correctness of the transformation. In the end, it classifies the failures into distinct bugs. We have evaluated this technique by testing up to 10 refactorings from Eclipse, NetBeans and the JastAdd Refactoring Tools. Our technique tested 153,444 transformations, and identified more than 100 bugs, which were reported to engines’ developers. They accepted most of them, and already fixed 35 bugs.