Fracture Analysis and Fatigue Strength Calculation of Anchor Bolt Used in Circulating Water Pump in Nuclear Power Plant

A circulating water pump is a key equipment of cooling systems in nuclear power plants. Several anchor bolts were broken at the inlet rings of the same type of pumps. The bolts were turned by a special material for seawater corrosion protection. There were obvious turning tool marks at the root of the thread, which was considered as the source of the crack. The fatigue crack extended to the depth of the bolt, causing obvious radiation stripes on the fracture surface, which was a typical fatigue fracture. Obvious overtightening characteristics were found at the head of the broken bolt. Fracture and energy spectrum analysis showed that the bolt was not corroded. The axial vibration of the pump was measured. The static tensile stress along the bolt axis caused by the preload, the axial tensile stress caused by the axial vibration, and the torsional stress were calculated, respectively. According to the fatigue strength theory, the composite safety factor of the bolt fatigue strength was 1.37 when overtightening at 1.2 times the design torque, which was less than the allowable safety factor of 1.5-1.8, so the bolt was not safe, which further verified the conclusion of fracture analysis. The reason for the low safety factor was caused by the overtightening force. The improvement method was to control the bolt preload or increasing the bolt diameter.

High Definition Metrology-Based Quality Improvement of Surface Texture in Face Milling of Workpieces with Discontinuous Surfaces

In face milling process, the quality of surface texture is vital for mechanical performance of workpieces. The quality of surface texture, especially for waviness, is directly affected by tool marks, a commonly observed phenomenon in face milling. However, appropriate approaches for evaluation and modeling of tool marks are absent to date. Limited to the resolution as well as the efficiency of conventional measurement instruments, the height data of tool marks is hard to be entirely obtained, leading to valuable information omission. Besides, most existing models of tool marks are established for general workpieces with regular geometry and continuous surfaces. Since the cutter-workpiece engagement mode has a significant impact on the generation of tool marks, current models could be inaccurate or invalid when dealing with workpieces with discontinuous surfaces. To overcome this shortage, a novel approach is proposed in this paper, aimed at quality improvement of surface texture in face milling of workpieces with discontinuous surfaces. Firstly, the evaluation indexes for tool marks are defined based on the recently developed high definition metrology (HDM). Secondly, the physical modeling of tool marks is presented, taking the face milling mechanism into account. Thirdly, the physical-informed optimization model is developed to search for the optimal processing parameters for surface quality improvement. At last, the effectiveness of the proposed approach is verified by a face milling experiment on the engine blocks.

Forensic Analysis and Interpretation of Tool Marks

The forensic analysis and interpretation of tool marks raise for consideration key methods and advances in the field of tool marks in forensic science. This chapter shows how tool mark analysis can be utilized in the course of criminal investigations. The focus of the chapter is on bringing together as much scientific knowledge in the area as possible in an accessible manner. It covers all aspects of tool mark evidence from the crime scene to the courtroom. This chapter provides information about tool marks in an effort to assist tool mark examiners as well as people practicing forensic science, crime scene examiners, crime investigating officers and members of the legal profession. It includes information about the analysis of tool marks at the crime scene and in the laboratory, the interpretation and assessment of challenges for examination and interpretation and also the way in which tool mark evidence can be presented in a courtroom.

Dual-Axial Tool Servo Diamond Turning of Hierarchical Micro-Nano-Structured Surfaces

This paper reports on a dual-axial tool servo diamond turning method for the one-step fabrication of hierarchical micro-nano-structured surfaces. With respect to the dual-axial servo motion (XZ), the z-axis motion can generate the primary surface with a complex shape, and the x-axis motion is used to synchronously form the secondary structure via controlling the residual tool marks. The toolpath determination algorithm for the developed turning method is described in detail, and the effect of the machining parameters on the basic feature and sizes of the generated secondary structures is investigated through conducting the numerical simulation for both toolpath and surface generation. The simulation result indicates that the additional x-axial motion is effective for the deterministic generation of a variety of secondary structures. Finally, taking advantage of an ultra-precision lathe with a self-developed tri-axial FTS, a hierarchical surface with high accuracy is practically generated.

Insights to enhance the examination of tool marks in human cartilage

This work deals with the examination of tool marks in human cartilage. We compared the effectiveness of several cleaning methods on cut marks in porcine cartilage. The method cleaning by multiple casts achieved the significantly highest scores (P = 0.02). Furthermore, we examined the grain-like elevations (dots) located on casts of cut cartilage. The results of this study suggest that the casting material forms these dots when penetrating cartilage cavities, which are areas where the strong collagen fibres leave space for the chondrocytes. We performed fixation experiments to avoid this, without success. In addition, 31 casting materials were compared regarding contrast under light-microscope and 3D tool marks scanner. Under the light-microscope, brown materials achieved significantly higher values than grey (P = 0.02) or black (P = 0.00) whereas under the 3D scanner, black materials reached higher contrast values than grey (P = 0.04) or brown (P = 0.047). To compare the accuracy and reproducibility of 6 test materials for cartilage, we used 10 knives to create cut marks that were subsequently scanned. During the alignment of the individual signals of each mark, the cross-correlation coefficients (Xmax) and lags (LXmax) were calculated. The signals of the marks in agarose were aligned with significantly fewer lags and achieved significantly higher cross-correlation coefficients compared to all tested materials (both P = 0.00). Moreover, we determined the cross-correlation coefficients (XC) for known-matches (KM) per material. Agarose achieved significantly higher values than AccuTrans®, Clear Ballistics™, and gelatine (all P = 0.00). The results of this work provide valuable insights for the forensic investigation of marks in human costal cartilage.

Turning parameter optimization for diffraction effect suppression of diamond-turned surface combining surface micro-topography model and scattering theory

The diamond-turning process is a mean optical surface generation technique with high figure accuracy and surface finish. The diamond-turned surface has a significant diffraction effect introduced by the tool marks remaining on the surface, which heavily degrade the optical performance in the visible wavelength spectrum. The traditional approach that was used to eliminate this effect was polishing. In this paper, we present a method to find turning parameters that can generate an optical surface without diffraction effect directly by coupling a surface micro-topography model of a turned surface via the scattering theory The surface micro-topography model of the turned surface reveals the relationship between tool marks and the diamond-turning parameters (DTPs). The scattering theory reveals the relationship between diffraction intensity distributions (DIDs) and surface micro-topography of the turned surface. Therefore, we obtained the relationship between DIDs and DTPs. The diffraction effect is considered to be eliminated when the first-order diffraction intensity is less than 0.01% of incidence intensity. The criterion of turning parameters for diffraction elimination is then obtained. Finally, turning experiments are performed to confirm the effectiveness of this method, and the diffraction-free surface finish is achieved.

Forenzná analýza stôp rezných nástrojov na kostiach

The article deals with the problem of forensic analysis of cutting tools traces on bones. It focuses on the assessment of macroscopic and microscopic structure of damaged tissue due to various cutting tools. It points out the need for teamwork of several experts in the analysis and evaluation of tool marks on the bones.

Advancements of the examination of tool marks in human cartilage

This work deals with the examination of tool marks in human cartilage. We compared the effectiveness of several cleaning methods on cut marks in porcine cartilage. The method cleaning by multiple casts achieved the significantly highest scores (P = 0.02). Furthermore, we examined the grain-like elevations (dots) located on casts of cut cartilage. The results of this study suggest that the casting material forms these dots when penetrating cartilage cavities, which are areas where the strong collagen fibers leave space for the chondrocytes. We performed fixation experiments to avoid this, without success. In addition, 31 casting materials were compared regarding contrast under light-microscope and 3D tool marks scanner. Under the light-microscope, brown materials achieved significantly higher values than grey (P = 0.02) or black (P = 0.00) whereas under the 3D scanner, black materials reached higher contrast values than grey (P = 0.04) or brown (P = 0.047). To compare the accuracy and reproducibility of 6 test materials for cartilage, we used 10 knives to create cut marks that were subsequently scanned. During the alignment of the individual signals of each mark, the cross-correlation coefficients (Xmax) and lags (LXmax) were calculated. The signals of the marks in agarose were aligned with significantly fewer lags and achieved significantly higher cross-correlation coefficients compared to all tested materials (both P = 0.00). Moreover, we determined the cross-correlation coefficients (XC) for known-matches (KM) per material. Agarose achieved significantly higher values than AccuTrans®, Clear Ballistics™, and gelatine (all P = 0.00). The results of this work provide valuable insights for the forensic investigation of marks in human costal cartilage.

Close up to the surface: reflections on a preliminary forensic study of four Chinese bronze mirrors

This article presents a generic, objective and evidence based forensic study of 4 very different Chinese bronze mirrors. The work was done within the Architectural Conservation Laboratory (ACLab), the Department of Physics, the Faculty of Medicine and also the Planetary Spectroscopy and Mineralogy Laboratory (PSML) all at the University of Hong Kong. The mirrors nominally cover the period of the Warring States (475–221 BC), Han (206 BC to 220 AD) and later Song (960–1279AD) dynasties. Comprehensive, mostly non-invasive, analytical methods and techniques were used. These included surface microscopy of tool marks, patina, corrosion and any residual archaeological evidence. Ultraviolet radiation examination, chemical spot testing and polarised light microscopy of ground-up patina samples was also done. More sophisticated “pXRF” X-ray fluorescence, “MARS” tomographic X-ray scanning and infrared spectroscopic analysis of the bronze alloys, corrosions and any earthen encrustations were also performed. This was to uncover as much forensic evidence as possible for these unprovenanced bronze mirrors. The results have revealed key metallurgical information of those four mirrors along with surface patina morphology and details of the corrosion and residual surface archaeology. A database on the physical condition of these mirrors has been established and burial/treatment history revealed. Mirrors 1 and 2 appear to have been heavily cleaned, polished and treated with abrasives in modern times. Mirror 2 in particular, has some problematic corrosion and inconclusive alloy composition. Mirror 3 and 4 both have archaeological evidence and no contrary forensic data that questions authenticity. Forensic study and verification of objects and artworks for academic purposes remains a legitimate and vital undertaking for universities, museums and national collections across the globe. Hence, the issue of authenticity when archaeological context is lacking is discussed. However, our key aim is to establish what can be learnt from technological, forensic investigation when studying bronze mirrors without further context and records, and what firm, generic evidence can be extracted from such close forensic examination to shed light on their true nature. We hope this will be useful for other researchers.