Finite-element-analysis of connection strength of assembled camshafts with different cam-bore profiles using tube hydroforming technology.

The assembled camshaft is a novel manufacturing product which connects the cam and the mandrel by tube hydroforming (THF) technology after they are processed separately. However, in the process of THF, the structure of the cam-bores has a crucial influence on the connection strength of the assembled camshafts. Therefore, three kinds of cam-bores with circular structure, isometric-trilateral profile and logarithmic spiral profile are selected for hydroforming with a hollow mandrel (tube) in this study. The finite-element-analysis is carried out by ABAQUS software, the variations of (residual) contact pressure and contact area under different structures are obtained, and the torsional angle variations after assembly are measured. Further, the connection strength of the assembled camshaft under three structures is discussed. The results show that the evaluation of connection strength of the assembled camshaft is affected by many factors, including contact pressure, maximum residual contact pressure, axial and circular residual contact pressure, contact area and its rate, residual contact area percentage and torsional angle. Through the comprehensive analysis of various factors, the torsional angle of the camshaft with circular structure is the largest, i.e. poor connection strength. By contrast, the torsional strength of the camshaft with isometric-trilateral profile is the largest, namely, the best connection strength.

Evaluation of Shear and Peel Strength of Al1060 Single-Lap and T-Lap Joints Produced by Rotated Clinching Process with Twin Rotating Punches.

The clinching process is widely used in joining lightweight sheet metal. We proposed a novel rotated clinching process (RCP), which is characterized by a flat bottom die structure and twin rotating punches. The aim of this study was to evaluate the strength of RCP joints. Al1060 sheets with thicknesses of 1.5 mm and 2 mm were used as the experimental materials. Overlap and T-lap RCP joints with three die depths and five bottom thicknesses were fabricated, and shear and peel tests were performed on the joints. The joint strengths were evaluated based on the mechanical load, cross-sectional profile dimensions, and failure mode. The results showed that the mechanical load is a direct, reliable, and quantitative evaluation criterion, while the cross-sectional profile and failure mode are indirect and qualitative. These criteria confirmed that the strength of thick sheet joints is higher than that of thin sheet joints, the shear strength is superior to the peel strength, and the strengths of the joints are high with failure mainly occurring due to tearing or shear failure. Finally, the key parameters for determining the strength of a joint include the bottom thickness/sheet thickness ratio (Rt), and the die depth (h).

[Preliminary clinical effect of proximal femoral nail anti-rotation to treat femoral intertrochanteric fractures].

OBJECTIVE: To evaluate the primary clinical effect of proximal femoral nail anti-rotation (PFNAR) in treating femoral intertrochanteric fractures, to summarize operation skills and to analyze correlated curative effective influential factors. METHODS: From July 2006 to May 2007, 19 cases of intertrochanteric fractures (including 8 males, 11 females, aged 45-87 years old) were treated with closed reduction and PFNAR fixation. Fractures were caused by falling. The locations were left sides in 10 cases and right sides in 9 cases. According to AO classification, there were 14 cases of type A2 and 5 cases of type A3. Operative time, volume of blood loss and weight bear time were analyzed, the condition of fracture union was observed and the hip function was evaluated using Harris criterion after 9 months of follow-up. RESULTS: Operative time ranged 23-78 minutes with an average time of 47 minutes, the volume of blood loss ranged 50-120 mL with an average volume of 85 mL, getting-out-of-bed time ranged 2-14 days with an average time of 7.4 days; the weight bearing time ranged 10-14 weeks with an average time of 12.4 weeks. No intra-operative femoral fractures and no regional or deep infection occurred during hospitalization period. Seventeen cases were followed up from 3 months to 12 months with an average time of 9.4 months, and achieved bone healing within 15-18 weeks with an average time of 16.5 weeks. No complications such as delay healing, coxa vara or coxa valga, cut-out and screw extraction occurred. Fifteen cases were followed up over 9 months; according to the Harris criterion for evaluation, the results were excellent in 13 cases, good in 1 case and fair in 1 case, the excellent and good rate was 93.3%. CONCLUSION: PFNAR has the advantages of micro invasion, easy-to-perform, less blood loss, less bone loss and stable fixation in treatment of unstable comminuted intertrochanteric fracture, especially in old patients with osteoporosis.

[Transtrochateric rotational osteotomy for osteonecrosis of the femoral head].

OBJECTIVE: To explore the indications, operative technique and clinical results of the transtrochanteric rotational osteotomy (TRO) for osteonecrosis of the femoral head (ONFH). METHODS: Nineteen patients (23 hips) with ONFH underwent TRO from October 1992 to May 2001 were reviewed. There were 14 males and 5 females. The age was ranging from 22 to 43 years old with an average age of 33.4 years old. The etiology were as followed: alcoholism 10 cases (12 hips); steroid 6 cases (7 hips); trauma 2 cases (2 hips); caisson disease 1 case (2 hips). Ficat stage: II 8 cases 8 hips; III 11 cases 15 hips. Harris hip score 46 to 74 with mean score 56 preoperatively. In order to determine the location and extent of osteonecrosis, A-P view and accurate lateral view (the film should be placed parallel to the femoral neck with the hip in precisely 90 degrees and flexion 45 degrees of abduction and neutral rotation) were taken in both hips preoperatively. The surgical technique described by Sugioka were used in all patients. RESULTS: Seventeen patients (19 hips) were followed up ranging from 18 to 11 years with mean 54 months. The Harris hip score was from 55 to 94 with mean 80.5. Fourteen hips score more than 80 and good to excellent rate was 73.2%. Harris score were less than 79 in 5 cases and 4 hips of these 5 hips were revised by total hip arthroplasty. The rotation angle was from 55 degrees to 80 degrees with mean 60 degrees . COMPLICATIONS: The circumflex femoral medial artery injury was found in 1 hip; subtrochanteric fracture was found in 2 hips and 1 osteotomy site nonunion occurred. CONCLUSION: TRO can be used to treat ONFH. The indications include: (1) younger patients (less than 45 years old). (2) Ficat stage II and III with more than one third intact articular surface of the femoral head. The better results could be obtained using posterior rotation and lager rotational angle. The Sugioka osteotomy should be used carefully because of its complicated surgical technique.