jquery遍历的radio的取值问题

html页面：
<c:if test="${courseStandardVos != null }">
        <c:set var="index" value="0"/>
        <c:forEach items="${courseStandardVos }" var="courseStandardVo">
            <tr>
                <td width="10%" align="center" valign="middle">${courseStandardVo.firstName}</td>
                <td width="10%" class="border_l" align="center" valign="middle">${courseStandardVo.secondName}</td>
                <td width="60%" align="left" valign="middle">${courseStandardVo.thirdName}</td>
                <c:set var="index" value="${index+1}"/>
                <td width="20%" align="center" valign="middle" name="grade" id="grade">
                    <input type="radio" id="score_five1" class="radio_ipt" name="radio${index}" value="5"/><label
                        for="score_five1">5</label>
                    <input type="radio" id="score_five2" class="radio_ipt" name="radio${index}" value="4"/><label
                        for="score_five2">4</label>
                    <input type="radio" id="score_five3" class="radio_ipt" name="radio${index}" value="3"/><label
                        for="score_five3">3</label>
                    <input type="radio" id="score_five4" class="radio_ipt" name="radio${index}" value="2"/><label
                        for="score_five4">2</label>
                    <input type="radio" id="score_five5" class="radio_ipt" name="radio${index}" value="1"/><label
                        for="score_five5">1</label>
                </td>
            </tr>
        </c:forEach>
    </c:if>

jquery代码：

$("#submitGrade").click(function () {
    $("#courseStandardVoId tr td").find("input[type='radio']").each(function(){
        if($(this).is(":checked")){
            alert($(this).val());
        }
    });
｝